Hello,

I am running Asterisk 11.12.0 on CentOS 6.4. The asterisk server and internal phones are located on the 10.10.32.0/21 LAN subnet. I have many internal SIP phones, which appear to be working correctly. I have a few external phones (Yealink SIP-T32G or other Yealink model) on 192.168.32.0/24 which have an OpenVPN client configured on them that connects back to the LAN network through a pfSense gateway with OpenVPN configured on it.

Asterisk server LAN IP: 10.10.32.10
My internal test phone: 146 at 10.10.32.96
My external test phone: 265 at 192.168.32.10

My sip.conf for these external users is as follows:
http://pastebin.com/2b9YE7Dz

The dialplan uses this Dial() invocation when dialing either an internal or external phone. Note that the max timeout is 12 seconds:
exten => _[12]XX,1,Dial(SIP/${EXTEN},12)

These external phones register correctly, and internal users can call these external users, the phones ring immediately, and the call is normal. However, if the external users try to dial an internal phone, I’ve observed some different failure modes:
* operating normally: sometimes the call rings immediately, the internal user answers, and the audio is present immediately
* ringing delay and no connection even after pickup: sometimes there’s a significant delay between when the call starts “ringing” on the external side and when it actually starts ringing on the internal user’s phone. Consequently, the internal user only has 1 or 2 rings to answer. Even if they do answer during this time, the line is dead and it goes to voicemail (the next step in the dialplan)
* delay before audio is connected after answer: sometimes the internal user answers, but there’s a delay of 3-10 seconds before either party can hear audio

I’ve enabled rtp and sip debug for this particular external phone (192.168.32.10) and attached console logs from both types of these failures:
* ringing delay and no connection even after pickup: http://pastebin.com/fe1khEmF
* delay before audio is connected after answer: http://pastebin.com/uZSMKczk

What else can I try to debug these problems? Since it is intermittent, I am not always able to reproduce (sometimes the calls work just fine).

Thanks,

Andrew Martin